[meteorite-list] Mammoth Stew

[E.P. Grondine]

Hi Sterling, list -

Thanks for clarifying the impact crater situation,
though I am still sceptical about the models of Moon
impact rates and Earth impact rates. 

I know that the Moon absorbed some impactors that were
headed for the Earth - at least it did so within human
recorded memory, and if anyone wants proof of this,
contact me off list and I'll you a copy of the
Trempeauleau petroglyph. 

So at a minimum the Earth cross section needs to be
reduced in modeling the combined Earth-Moon system. My
guess is that this should reduce the impact
rate/craters by about 10%, leaving say only 2.7
million or so craters. (Imagine that, E.P. arguing for
a lower Earth impact rate!)

Could you give us the quick math for this? I can't do
it myself anymore.

I was also quite surprised by this cratering model you
pointed to:

http://www.news.uiuc.edu/scitips/02/1025craters.html

given that the KT-fossil meteorite is carbonaceous
chondrite, in other words a comet, and that the
Sudbury impact appears to have been iron, as its
remains are a source for our nickel steel. It seems
likely to me that this Illinois team's computer model
is off.

Re: the apparent 31,000 BCE impact, my hope is that
large irons may have survived in "defraction lenses"
(is that the right term?) in the blast, irons large
enough to survive later weathering. Trying to remember
the find spot for the mammoth tusks, I seem to
remember it was reported that they came from a shop in
Calgary, further unknown.

good hunting all, 
E.P. Grondine
Man and Impact in the Americas




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